From Tokyopop:
After the 5th World War comes to an end, 46% of humans have been wiped off the face of the earth. Because of contamination, the survivors of this war colonize the moon and Mars with plans to move back to Earth after they purify the planet.

From Tokyopop:
After the 5th World War comes to an end, 46% of humans have been wiped off the face of the earth. Because of contamination, the survivors of this war colonize the moon and Mars with plans to move back to Earth after they purify the planet.